Barnes's Psalms 107:29 Bible Commentary

He maketh the storm a calm - God does this, and God only can do it. The fact, therefore, that Jesus did it Matthew 8:26, proves that he was divine. There can be no more striking proof of divine power than the ability to calm the raging waves of the ocean by a word. This is literally, "He places the tempest to silence."

So that the waves thereof are still - Are lulled. The ocean ceases to be agitated, and the surface becomes smooth. Nothing is more still than the ocean in a calm. Not a breath of air seems to stir; not a ripple agitates the surface of the sea; the sails of the vessel hang loose, and even the vessel seems to be perfectly at rest: "As idle as a painted ship upon a painted ocean." So God can calm down the tempest of the soul. He can make the mind which was heaving and tossed, like the ocean, with anguish on account of guilt, and which trembled in view of the coming judgment, as calm as the ocean is when in its state of perfect repose. God can do "this," and none "but" God can do it; and as Jesus thus stills the agitation of the guilty soul, as he did the waves of the sea, "this" proves also that he is divine.